Electron beam apparatus and lens array

Abstract

There is provided both an electron beam apparatus and a lens array, capable of correcting a curvature of field aberration under various optical conditions. The electron beam apparatus comprises the lens array having a plurality of electrodes, and multiple openings are formed in the respective electrodes. An opening diameter distribution with respect to the respective opening diameters of the plural openings formed in the respective electrodes are individually set, and voltages applied to the respective electrodes are independently controlled to thereby independently adjust an image forming position of a reference beam, and a curvature of the lens array image surface.

Description

CLAIM OF PRIORITY[0001]The present application claims priority from Japanese patent application JP 2012-063816 filed on Mar. 21, 2012, the content of which is hereby incorporated by reference into this application.FIELD OF THE INVENTION[0002]The present invention relates to an electron beam application technology, and in particular, to an electron beam apparatus such as an inspection apparatus, a microscope, and so forth, used in a semiconductor process, and a lens array incorporated therein.BACKGROUND OF THE INVENTION[0003]In a semiconductor process, use is made of an electron microscope for irradiating an electron beam called a primary beam onto a specimen to thereby make an observation of a pattern, and a structure, formed on the specimen such as a wafer, and so forth from a signal of a secondary electron, a reflection electron, and so forth (hereinafter called a secondary beam), that is, to carry out observation, measurement, inspection, and suchlike. The electron beam apparatus...

AI Technical Summary

Benefits of technology

The invention provides a solution for correcting the curvature of field aberration of an objective lens in an electron beam apparatus. The lens array has the ability to individually control the shape of its image-forming surface in response to changes in various parameters. This allows for the correction of the curvature of field under different optical conditions, provided that the position of the electron beam and its relation to the center of the lens array remains unchanged. The technical effect of this invention is the ability to correct the curvature of field under various optical conditions. Additionally, the lens array is designed to have a unit that can independently adjust the image forming position of one length of electron beam among the plural electron beams, serving as a reference, and the curvature of the image-forming surface. This further enhances the ability to correct the curvature of field under different optical conditions.

Problems solved by technology

In the case of correcting the curvature of field aberration of an objective lens using, for example, the scheme disclosed in Japanese Unexamined Patent Application Publication No. 2007-123599, a likely problem will be that the diameter of the opening of the lens array cannot be easily changed, and therefore, an optical condition under which the curvature of field can be corrected will be restricted.

More specifically, if a magnification of the objective lens is changed after once the lens array is installed in the apparatus, it will be difficult to control the curvature of field of the objective lens so as to match a change in the curvature of field aberration of the objective lens, accompanying a change in the magnification.

However, in reality, many technical problems are involved in preparing the lens array described in Japanese Unexamined Patent Application Publication No. 2001-267221.

Further, in consideration of many power supplies, and circuits, necessary in order to control voltages applied to the respective electron beams, it can be said that this method has a problem from a cost point of view, as well.

Images